No they don't give instructions about wake turbulence, but they position following aircraft behind at a minimum distance to avoid the wake turbulance from the proceeding aircraft using headings and speeds. In a busy airport like Heathrow the distances have to be spot on, so they can move as much aircraft as possible. Aircraft are split into wake turbulence categories, Heavy, medium, small and light based on their weight, plus a special one for the A380! you are right that there will be a bigger gap behind heavier aircraft for smaller aircraft ie, 747 followed by 747 = 4 miles, 747 followed by A320 = 5 miles A320 follwed by A320 = no vortex issue, but radar seperation used etc, but where possible the controllers may try and group heavies together then smaller aircraft as this saves lots of larger gaps and gets more aircraft on the ground in a given time. The ILS "glideslope" does not vary, it is at an angle of 3 degrees. Aircraft use flaps to allow the aircraft to fly at a slower speed on landing, airbrakes / spoilers are used after touchdown to aid braking. With flaps & wheels down more power will be used on approach than if they were up due to the extra drag, but not full power, if it were then they wouldn't be able to go around. (ailerons btw are what is used to roll / bank the aircraft) That's a simplistic view anyway...